The invention of the present application relates generally to methods and apparatus for controlling execution of a remote application over the Internet and, in particular, receiving data from an input device over a computer network.
The introduction of networks, such as LANs, WANs, and the Internet, has revolutionized the field of computing and, in particular, inputting and outputting to other devices. Early computer workstations included a personal computer electrically connected to input and output devices, such as printers, scanners, fax machines, and cameras. Today, networks allow multiple computer workstations or personal computers (collectively called “clients”) to share input or output devices.
To share resources across a network, the resources must be able to communicate using the same or compatible protocols. Conventional networks are organized as a series of layers, the numbers, names, contents, and function of which differ from network to network. In most conventional networks, however, each layer offers services to the higher layers while shielding those layers from the details of how the offered services are actually implemented. When machines communicate, the layers on each machine can communicate with an equivalent layer on other machines using the appropriate protocol for that layer. The protocols used by the layers of a system is referred to as a “protocol stack” and define the network environment. In an UNIX environment, for example, the Transmission Control Protocol/Internet Protocol (TCP/IP) protocol stack includes the transmission control protocol (TCP) and Internet protocol (IP). Server Message Block (SMB) is a protocol stack for passing information between network computers for processing by a device. The TCP/IP protocol stack is one of the most common protocols used on the Internet.
FIG. 1 shows a conventional printing system including multiple clients and a shared printing device. Clients 105, 110, and 115 are connected via network 118 to a shared server 120 and printer 135. Any of clients 105, 110, and 115 may use printer 135 via server 120. If client 105 wants to print, for example, it sends, or “pushes,” a print job consisting of print commands and print data over network 118 to server 120. Server 120 stores the print job to a disk, queue, or “spool,” 125 in server 120. As a print job percolates to the top of the print queue, print controller 130 reads the stored file from spool 125 and transmits the file to printer 135. Print controller 130 also sends commands to printer 135. In response, printer 135 processes the received file.
Conventional scanners also operate using “push” technology. Using a conventional scanner, for example, a document is scanned and an image file is created. The image file may be stored in memory on the scanner or sent to another remote device. The image file may be transmitted across a network using any conventional protocol or, for example, by attaching the image file to an electronic mail message. In conventional scanning devices, however, the image file is transmitted to, or “pushed,” to any remote devices.
This conventional “push” technology has some limitations. In a conventional printing or scanning system, for example, clients transmit command information as well as a digital copy of the image file across the network to the destination. The receiving device must therefore have sufficient disk space in the spool to store the image files when they are received. In networks with many clients, a print server requires large amounts of costly disk space, and may delay accepting new jobs if the disk's spool has reached its maximum storage capacity. When the spool is full, the client may waste time querying the server and waiting for it to have sufficient space to receive the job. Furthermore, the client may be inoperable for other tasks until the server can process the job, which can be a significant period of time if the output file is very large. When a conventional scanner sends scanned image files to a destination without first communicating with the destination device, scanned image files may be lost or may exceed the file storage limit of the destination device.
Furthermore, network devices that receive data from or transmit data to clients on a variety of platforms require multiple protocols and are more difficult to implement and troubleshoot. A platform is any piece of hardware plus its software operating system. FIG. 2 illustrates a conventional scanner 210 that transmits scanned images to clients 230, 240, and 250, each operating on a different platform. Client 230 may be an Apple Macintosh using the MacOS® operating system, client 240 may be a PC using the UNIX operating system, and client 250 may be a PC operating the Windows 95® operating system. A scanner that transmits scan jobs to clients on different platforms requires multiple protocol stacks to interpret and output the print request. For example, as shown in FIG. 2, scanner 210 must contain TCP/IP 214, SMB 216, and PAP (Printer Access Protocol) 212 protocol stacks to communicate with the various clients 230, 240, and 250 on the network A scanner that must be configured to use a multitude of protocols is very complex, requiring additional time and resources to develop, troubleshoot, and maintain.